A blind rivet has an outer normally tubular body formed at one end with a head and provided internally with a rivet core or mandrel. The mandrel is gripped by a chuck of the riveting tool which is then operated to pull this chuck away from a fixed tip to pull the head of the rivet against this tip, and then to pull the mandrel though the rivet to upset the far end of it. The mandrel is normally constructed to break when tensioned to a predetermined limit corresponding to a predetermined deformation or upsetting of the rivet and depending on the rivet material.
For production use such blind riveters are normally operated pneumatically, hydraulically, or with combined air and hydraulic systems. The details of the operation of such riveters can be seen in U.S. Pat. Nos. 4,005,598; 4,027,520; and 4,050,285.
It is known to form the back of the head of such a riveting tool with a compartment for receiving the mandrels after they have been pulled from the respective rivets. In the simplest system a throughgoing passage extends from the chuck back into this empty compartment, so that as new mandrels are inserted in the chuck the old ones are pushed upwardly. Normally the operator of the tool turns the device over and bumps it on the top of the storage compartment to move the old mandrel out of the chuck and into this compartment. Such an arrangement, although somewhat tedious to operate, nonetheless eliminates the necessity of cleaning up all the mandrels after a large riveting job.
Accordingly it has been suggested to provide a pneumatic conveying system inside the riveter which is connected to a passage immediately at the head or tip of the riveter so that a current of air blows the mandrel back into the storage compartment at the end of the riveting operation. Such a system requires a complicated connection to the tip or working head of the riveter, and normally requires the pulling chuck to be at least partially rebuilt to accommodate the new pneumatic system. Another disadvantage is that the air blown into the passage through the chuck moves in both directions, resisting insertion of a new mandrel just as it aids in moving the old mandrel along to the storage compartment. Thus a new rivet must be carefully inserted into the tool which must then be briefly actuated to tightly grip the new rivet before the worker can release it with his or her fingers.